Object information acquiring apparatus

ABSTRACT

Provided is an object information acquiring apparatus including: detecting elements converting an acoustic wave propagated from an object to an electric signal, a processing unit acquiring characteristic information of the object using the electric signal, a supporting unit supporting the detecting elements, an input unit receiving information concerning three-dimensional region of interest, a display controlling unit displaying a predetermined three-dimensional shape representing, a scanning region setting unit setting a scanning region, and a scanning unit moving the supporting unit, wherein the display controlling unit changes the size of the region of interest stepwise by using a feature value peculiar to the apparatus as a unit based on the inputted information, and displays the changed region of interest.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an object information acquiringapparatus.

2. Description of the Related Art

As a technique for imaging the inside of an object using an acousticwave (typically, an ultrasound wave), a photoacoustic imaging method hasbeen proposed. The photoacoustic imaging method is a method ofvisualizing information related to an optical characteristic value onthe inside of an object using an acoustic wave generated by irradiatingthe object with pulsed laser light.

U.S. Pat. No. 5,713,356 describes a method of receiving an ultrasoundwave from an object (a breast) using a plurality of transducers disposedon a hemisphere and generating three-dimensional image data (imagereconstruction). In an apparatus described in U.S. Pat. No. 5,713,356,an examinee inserts a breast into a detector, in which hemisphericaltransducers are disposed, and takes a face-down posture. Water fortaking acoustic matching is filled between the inserted breast and thetransducers. During measurement, the detector, in which the transducersare provided, rotates stepwise. The transducers receive acoustic wavesin positions in respective steps. By scanning the detector in this way,even with a small number of the transducers, it is possible to performthe measurement as if the transducers were present in many directions.The breast is inserted to be located near the hemispherical center ofthe detector. Pulsed light is irradiated from a hemispherical vertexportion of the detector.

Patent Literature 1: U.S. Pat. No. 5,713,356

SUMMARY OF THE INVENTION

In the case of the apparatus that scans the detector as in U.S. Pat. No.5,713,356, it is desired that a user can designate a region where theuser desires to acquire characteristic information in the object (aregion of interest (ROI)) out of an entire region that can be scanned.In particular, in the case of an apparatus that takes an excessivelylong time to measure the entire region, in order to reduce themeasurement time, there is a demand for a function for performingmeasurement of only a designated region of interest.

In an apparatus that generates three-dimensional image data like theapparatus of U.S. Pat. No. 5,713,356, it is preferable that the regionof interest can also be three-dimensionally designated. However, sinceconventional setting operation for a three-dimensional region ofinterest is complicated, there is a demand for a method of simplydesignating a three-dimensional region.

The present invention has been devised in view of such problemrecognition. It is an object of the present invention to provide atechnique for enabling a user to easily set a three-dimensional regionof interest.

The present invention provides an object information acquiring apparatuscomprising:

-   -   a light source;    -   an irradiating unit configured to irradiate an object with light        from the light source;    -   a plurality of detecting elements configured to detect an        acoustic wave propagated from the object and output an electric        signal;    -   a processing unit configured to acquire characteristic        information of an inside of the object using the electric        signal;    -   a supporting unit configured to support the plurality of        detecting elements;    -   an input unit capable of receiving an input of information        concerning a region of interest, which is a three-dimensional        region where the characteristic information is to be acquired;    -   a display controlling unit configured to cause a display unit to        display a predetermined three-dimensional shape representing the        region of interest;    -   a scanning region setting unit configured to set a scanning        region on the basis of the region of interest; and    -   a scanning unit configured to move the supporting unit in the        scanning region, wherein    -   the display controlling unit changes, on the basis of the        information concerning the region of interest input from the        input unit, a size of the region of interest stepwise by using a        feature value peculiar to the apparatus as a unit, and causes        the display unit to display the region of interest after the        change.

According to the present invention, it is possible to provide atechnique for enabling a user to easily set a three-dimensional regionof interest.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of an apparatusaccording to a first embodiment;

FIGS. 2A and 2B are diagrams showing a sensitivity characteristic of anacoustic detecting element according to the first embodiment;

FIG. 3 is an example of an initial screen for designating a region ofinterest according to the first embodiment;

FIG. 4 is an XY sectional view of a typical shape of the region ofinterest according to the first embodiment;

FIG. 5 is an explanatory diagram of an XY sectional shape of the typicalshape of the region of interest according to the first embodiment;

FIG. 6 is a size change explanatory diagram of the typical shape of theregion of interest according to the first embodiment; and

FIG. 7 is a flowchart for explaining processing according to the firstembodiment.

DESCRIPTION OF THE EMBODIMENTS

A preferred embodiment of the present invention is explained below withreference to the drawings. However, the dimensions, the materials, theshapes, a relative arrangement, and the like of components describedbelow should be changed as appropriate according to the configurationand various conditions of an apparatus applied with the invention andare not meant to limit the scope of the present invention to thedescription explained below.

The present invention relates to a technique for detecting an acousticwave propagated from an object, generating characteristic information ofthe inside of the object, and acquiring the characteristic information.Therefore, the present invention is grasped as an object informationacquiring apparatus or a control method therefor, an object informationacquiring method, or a signal processing method. The present inventionis also grasped as a computer program for causing an informationprocessing apparatus including hardware resources such as a CPU toexecute these methods or a storage medium having the computer programstored therein. The present invention is also grasped as an acousticwave measuring apparatus or a control method therefor.

The object information acquiring apparatus of the present inventionincludes an apparatus that makes use of a photoacoustic tomographytechnique for irradiating an object with light (an electromagnetic wave)and receiving (detecting) an acoustic wave generated in a specificposition in the object or the surface of the object and propagatedaccording to a photoacoustic effect. Such an object informationacquiring apparatus obtains characteristic information inside the objectin a form of image data or the like on the basis of photoacousticmeasurement. Therefore, the object information acquiring apparatus canbe called photoacoustic imaging apparatus and photoacousticimage-forming apparatus.

Characteristic information in a photoacoustic apparatus indicates ageneration source distribution of an acoustic wave generated by lightirradiation, an initial sound pressure distribution in the object, anoptical energy absorption density distribution or an absorptioncoefficient distribution derived from the initial sound pressuredistribution, or a concentration distribution of a substance forming atissue. Specifically, the characteristic information is anoxygenated/reduced hemoglobin concentration distribution, a bloodcomponent distribution such as an oxygen saturation degree distributioncalculated from the oxygenated/reduced hemoglobin concentrationdistribution, a distribution of fat, collagen, or moisture, or the like.The characteristic information may be calculated as distributioninformation of positions in the object rather than as numerical valuedata. That is, distribution information of the absorption coefficientdistribution, the oxygen saturation degree distribution, or the like maybe set as object information.

The acoustic wave in the present invention typically means an ultrasoundwave and includes an elastic wave called sound wave or acoustic wave.The acoustic wave generated by the photoacoustic effect is calledphotoacoustic wave or light-induced ultrasound wave. An electric signalconverted from the acoustic wave by a probe is also called acousticsignal.

As the object in the present invention, a breast of a living organism ismainly assumed. However, the object is not limited to this. Measurementof other segments of the living organism and a non-living organismmaterial is also possible.

First Embodiment Spiral Scan Type

A schematic diagram showing the configuration of a photoacousticapparatus in a preferred embodiment of the present invention is shown inFIG. 1.

The photoacoustic apparatus (hereinafter also simply referred to as“apparatus”) shown in FIG. 1 acquires characteristic information of anobject E (a breast) and creates an image of the inside of the object E.The photoacoustic apparatus in this embodiment includes, as components,a light source 100, an optical system 200 functioning as a lightirradiating unit, an acoustic detecting element 300, a supporting unit400, and a region-of-interest designating unit 500 functioning as aninput unit. The photoacoustic apparatus further includes a displaycontrolling unit 600, a scanning region setting unit 700, a scanner 800functioning as a scanning unit, a signal processing unit 900, and anacoustic matching material 1000. Reference numeral 601 denotes a displayunit.

The object and the components are explained below.

Object

Although the object E is a target of measurement and is not a componentconfiguring the apparatus, the object E is explained below. Specificexamples of the object E include a living organism such as a breast anda phantom simulating an acoustic characteristic and an opticalcharacteristic of the living organism used for adjustment and the likeof the apparatus. The acoustic characteristic is typically propagationspeed and an attenuation ratio of an acoustic wave. The opticalcharacteristic is typically an absorption coefficient and a scatteringcoefficient of light. A light-absorbing body having a large lightabsorption coefficient is present on the inside of the object. In theliving organism, hemoglobin, water, melanin, collagen, lipid, and thelike are light-absorbing bodies. In the phantom, a substance simulatingthe optical characteristic is encapsulated on the inside as alight-absorbing body.

Light Source

The light source 100 is a device that generates pulsed light. In orderto obtain a large output, a laser is desirable as the light source.However, the light source may be a light-emitting diode or the like. Inorder to effectively generate a photoacoustic wave, it is preferable toirradiate an object with light in a sufficiently short time according toa thermal characteristic of the object. When the object is a livingorganism, it is desirable to set pulse width of the pulsed lightgenerated from the light source 100 is set to several tens nanosecondsor less. Wavelength of the pulsed light is a near infrared region calledwindow of the living organism and is desirably approximately 700 nm to1200 nm. Light in this region reaches a relatively deep part of theliving organism. Therefore, information concerning a deep part insidethe object can be acquired. If the measurement is limited to measurementof a living organism surface portion, visible light of approximately 500nm to 700 nm to the near infrared region may be used. Further, thewavelength of the pulsed light desirably has a high absorptioncoefficient with respect to an observation target.

Optical System

The optical system 200 is a device that leads the pulsed light generatedby the light source 100 to the object E. Specifically, the opticalsystem 200 is an optical device such as a lens, a mirror, a prism, anoptical fiber, or a diffusion plate or a combination of these devices.When the light is led, the shape and the light density of the light aresometimes changed to obtain a desired light distribution using theseoptical devices. Optical devices are not limited to the optical devicesdescribed above and may be any optical devices as long as the opticaldevices satisfy such functions. The optical system is equivalent to anirradiating unit of the present invention.

Note that, as the intensity of light permitted to be irradiated on aliving organism tissue, a maximum permissible exposure (MPE) is decidedby a safety standard. As the safety standard, there is IEC 60825-1:Safety of laser products. Besides, there are JIS C 6802: safety standardof laser products, FDA: 21 CFR Part 1040.10, ANSI Z136. 1: Laser SafetyStandards, and the like. The maximum permissible exposure specifies theintensity of light that can be irradiated per unit area. Therefore, inorder to obtain a satisfactory object internal image while observing themaximum permissible exposure, it is preferable to collectively irradiatelight on the surface of the object E in a wide area. Consequently, it ispossible to lead a lot of light to the object E while suppressing lightintensity per unit area. Therefore, reception of a photoacoustic wave ata high SN ratio is possible. Therefore, it is preferable to spread lightto a certain degree of an area as indicated by a broken line extendingfrom the optical system 200 shown in FIG. 1 rather than condensing thelight with a lens.

Acoustic Detecting Element

The acoustic detecting element 300 receives a photoacoustic wave andconverts the photoacoustic wave into an electric signal. The acousticdetecting element 300 is desirably an acoustic detecting element havinghigh reception sensitivity and a wide frequency band with respect to thephotoacoustic wave from the object E. As a member forming the acousticdetecting element 300, a piezoelectric ceramic material represented bylead zirconate titanate (PZT), a polymer piezoelectric film materialrepresented by polyvinylidene fluoride (PVDF), and the like can be used.An element other than the piezoelectric element may be used. Forexample, an element of a capacitance type such as a capacitivemicro-machined ultrasonic transducer (cMUT), an acoustic detectingelement including a Fabry-Perot interferometer, and the like can beused.

The acoustic detecting element 300 has an axial direction in whichreception sensitivity increases. A reception region where thephotoacoustic wave is received at high sensitivity is formed in theaxial direction. In the following explanation, “the axial direction inwhich reception sensitivity increases” is described as “directionalaxis”.

FIG. 2A is a diagram showing an example of a sensitivity characteristicof the acoustic detecting element 300. As shown in FIG. 2B, the acousticdetecting element 300 typically includes a circular planar receptionsurface. FIG. 2A shows, with an incident angle of incidence of aphotoacoustic wave from the normal direction of the reception surfaceset to 0 degree, a sensitivity characteristic corresponding to theincident angle on a cross section passing the center line of theacoustic detecting element 300 shown in FIG. 2B. In the example shown inFIG. 2A, sensitivity in the case of the incidence from the normaldirection of the reception surface is the highest. The sensitivitydecreases as the incident angle increases.

The incident angle at the time when the sensitivity is a half S/2 of amaximum S is represented as α. In this embodiment, a region where thephotoacoustic wave is made incident on the reception surface of theacoustic detecting element 300 at an angle equal to or smaller than theincident angle α is a region where the photoacoustic wave can bereceived at high sensitivity. In the following explanation, “the regionwhere the photoacoustic wave can be received at high sensitivity” isdescribed as “high-sensitivity reception region”. In this way, theacoustic detecting element 300 has the directional axis. Thehigh-sensitivity reception region where the photoacoustic wave isreceived at high sensitivity is formed around the directional axis.

Note that the shape of the reception surface of the acoustic detectingelement 300 is not limited to this. The reception sensitivity may have adirection characteristic.

Supporting Unit

The supporting unit 400 shown in FIG. 1 is a substantially hemisphericalcontainer. A plurality of acoustic detecting elements 300 are set on thesurface on the inner side of the hemisphere. The optical system 200 isset in a lower part (a pole) of the hemisphere. On the inner side of thehemisphere, a solution is filled as the acoustic matching material 1000explained below. The acoustic detecting elements 300 are connected to asignal processing unit 900 explained below by a not-shown lead wire. Theshape of the supporting unit 400 is not limited to the hemisphere. Aspherical crown shape, a shape obtained by cutting a part of anellipsoid, a shape obtained by combining a plurality of planes or curvedsurfaces, and the like can also be used. As explained below, the shapeof the supporting unit 400 only has to be a shape that can support aplurality of acoustic detecting elements such that directional axes ofat least a part of the plurality of acoustic detecting elementsconverge.

The supporting unit 400 is preferably configured using a metal materialhaving high mechanical strength in order to support these members. It ispreferable to provide a sealing member for preventing the acousticmatching material 1000 from leaking to the outer side of the supportingunit 400. A member that holds the object E may be provided in an upperpart of the supporting unit 400. The holding member suitably has a cupshape or a bowl shape. The holding member desirably has transmissivityto light from the irradiating unit and a photoacoustic wave from theinside of the object.

When elements are arrayed in an array shape on the hemispherical surfaceof the supporting unit 400, directional axes of at least a part of theplurality of acoustic detecting elements 300 form an angle differentfrom directional axes of the other elements. The directional axes of theelements cross in a region substantially in the center of thehemisphere. FIG. 1 is a sectional view taken along a vertical surfacepassing the center of the hemisphere. Alternate long and short dashlines converging on a part of a region in the object E indicate thedirectional axes of the acoustic detecting elements 300. The opticalsystem 200 is arranged to illuminate the region substantially in thecenter of the hemisphere. In the case of such an arrangement, in animage obtained by universal back projection, the resolution is high inthe center of the hemisphere and decreases away from the center.Position information of the acoustic detecting elements 300 and theoptical system 200 in the supporting unit 400 is stored in a not-shownrecording device such as a memory and used when an image is generated.

In this specification, such a region having high resolution is referredto as high-resolution region. In this embodiment, the high-resolutionregion indicates a region from a point where the resolution is thehighest to a point where the resolution is a half of the highestresolution. In FIG. 1, a region G is equivalent to the high-resolutionregion. Note that directions in which sensitivities of the acousticdetecting elements are the highest do not always have to cross as longas directions in which reception sensitivities are high are directed toa specific region and a desired high-resolution region can be formed. Apart of the plurality of acoustic detecting elements supported by thesupporting unit only have to be directed to the specific region.

Region-of-Interest Designating Unit

The region-of-interest designating unit 500 is input means for the userto designate a three-dimensional region of interest. That is, theregion-of-interest designating unit 500 can receive an input ofinformation concerning a region of interest, which is athree-dimensional region. The user designates the region of interestwhile referring to a photographed image of the object E displayed on thedisplay unit 601. As the photographed image of the object E at thispoint, an image photographed by a not-shown capture camera is displayed.The region-of-interest designating unit 500 may be a pointing devicesuch as a mouse or a keyboard, a pen tablet type device, or a touch padattached to the surface of the display unit 601. The display unit 601may be configured by a touch panel. The region-of-interest designatingunit 500 is equivalent to an input unit of the present invention.

Further, on the display unit 601, a typical shape of the region ofinterest displayed by the display controlling unit 600 is displayed tobe superimposed on the photographed image of the object E. In theregion-of-interest designating unit 500, an instruction input forchanging the size of the typical shape and designating the position ofthe typical shape is performed. In this embodiment, as the size changeinstruction for the typical shape, a size increase or reductioninstruction is performed. The size of the typical shape of thethree-dimensional region of interest can be changed stepwise. Thetypical shape corresponds to a predetermined three-dimensional shape inthe present invention.

Display Controlling Unit

The display controlling unit 600 outputs information for performing thedisplay of the typical shape of the region of interest designated by theuser. As an initial screen for the region of interest designation, thedisplay controlling unit 600 displays the typical shape of the region ofinterest in a predetermined size. The display controlling unit 600generates a display image of the region of interest according to a sizechange instruction and a position change instruction from theregion-of-interest designating unit 500. In response to the size changeinstruction, the display controlling unit 600 generates imageinformation in which the size of the typical shape of the region ofinterest is changed stepwise with a predetermined change amount. Inresponse to the position change instruction, the display controllingunit 600 generates image information in which the display position ischanged within a photographable range.

The display controlling unit 600 in this embodiment includes a regioncalculating unit that converts a display coordinate system and ascanning coordinate system. The display controlling unit 600 oncechanges, on the basis of the scanning coordinate system, the positionand the size of the region of interest that is changed according to aposition change and a size change of the three-dimensional region ofinterest designated by the region-of-interest designating unit. Thedisplay controlling unit 600 outputs, using the region calculating unit,image data of the display coordinate system such that screen displaysuitable for the display unit 601 is performed.

A scan track in this embodiment is a spiral track on an XY plane. Thatis, in this embodiment, photoacoustic measurement is performed such thata moving distance is an equal interval while spirally moving thesupporting unit. Note that the spiral movement indicates that the entiresupporting unit spirally moves and does not indicate that a rotationalmotion of the supporting unit with the center fixed like a top.Consequently, measurement is performed such that the high-sensitivityregion is located at an equal interval in the measurement region. Theinfluence of sensitivity unevenness in the measurement can be reduced.For the same purpose, an interval of circumferences (a circumferentialpitch) of the spiral is also an equal interval. In this embodiment, thecircumferential pitch of the spiral is set to a 10 mm pitch. In thiscase, the shape of an overall region of a high-resolution region formedby relatively spirally scanning the high-resolution region with respectto the object can be approximated to a column. Therefore, the typicalshape of the region of interest in this embodiment is a columnar shape.Note that the circumferential pitches of the spiral scanning may bedifferent rather than the equal interval.

In this embodiment, the typical shape is the columnar shape to simplifyexplanation. However, the typical shape may be a shape accuratelyrepresenting an overall shape of the high-resolution region formed bythe scanning or may be approximated to another shape. For example, theoverall shape of the high-resolution region can also take a complicatedshape obtained by rounding a flexible cylinder in a spiral shape. If thecircumferential pitch of the spiral track increases, the overall shapeof the high-resolution region is more complicated. These complicatedshapes may be approximated by a column as long as there is no largedifference in outlines or may be approximated as a flat barrel shape asanother shape example.

Scanning Region Setting Unit

The scanning region setting unit 700 is a device that sets scanningregions in X, Y, and Z directions in which the supporting unit 400 ismoved. The scanning region setting unit 700 sets X, Y, and Z regions inwhich the supporting unit 400 is moved such that the three-dimensionalregion of interest set by the region-of-interest designating unit 500 isincluded inside a track range of the high-resolution region G formed byscanning the supporting unit 400 in the X, Y, and Z directions. In thisembodiment, a system for calculating a Z coordinate position in whichthe region of interest fits and spirally scanning the XY plane isadopted.

Note that, when scheduling scanning of the detector on the basis of theset region of interest, the scanning region setting unit 700 preferablysets, as the scanning region, a region slightly wider than the region ofinterest. This is because, to satisfy desired image quality concerningthe set region of interest, it is preferable to acquire an acoustic wavefrom the periphery of the region of interest. However, compared with ameasurement time assumed from the set region of interest, an actualmeasurement time of the scanning region more often increases.

Scanner

The scanner 800 is a device that moves the position of the supportingunit 400 in the X, Y, and Z directions in FIG. 1 to thereby change theposition of the supporting unit 400 with respect to the object E.Therefore, the scanner 800 includes guide mechanisms in the X, Y, and Zdirections, driving mechanisms in the X, Y, and Z directions, and aposition sensor that detects the positions in the X, Y, and Z directionsof the supporting unit 400, all of which are not shown in the figure. Asshown in FIG. 1, since the supporting unit 400 is mounted on the scanner800, it is preferable to use, as the guide mechanisms, linear guides orthe like resistible against a large load. As the driving mechanisms,lead screw mechanisms, link mechanisms, gear mechanisms, hydraulicmechanisms, and the like can be used. For a driving force, a motor orthe like can be used. As the position sensor, an encoder, apotentiometer including a variable resistor, and the like can be used.The scanning unit of the present invention corresponds to the scanningregion setting unit and the scanner.

Signal Processing Unit

The signal processing unit 900 has a function of storing electricsignals input from the acoustic detecting elements 300. The signalprocessing unit 900 has a function of generating characteristicinformation such as an optical characteristic in the object E using theelectric signals input from the acoustic detecting elements 300 andgenerating an image of the inside of the object E on the basis of thecharacteristic information. Further, the signal processing unit 900 hasa function of operating the photoacoustic apparatus such as lightemission control of the light source 100 and driving control of thescanner 800.

An arithmetic unit of the signal processing unit 900 is typicallyconfigured from an element such as a CPU, a GPU, or an A/D converter anda circuit such as an FPGA or an ASIC. Note that the arithmetic unit maybe not only configured from one element and one circuit but alsoconfigured from a plurality of elements and a plurality of circuits. Anyone of the elements and any one of the circuits may execute kinds ofprocessing performed by the signal processing unit 900.

A storing unit in the signal processing unit 900 is typically configuredfrom a storage medium such as a ROM, a RAM, or a hard disk. Note thatthe storing unit may be not only configured from one storage medium butalso configured from a plurality of storage media.

The signal processing unit 900 is preferably configured to be capable ofsimultaneously pipeline-processing a plurality of signals. Consequently,it is possible to reduce time until object information is acquired.

Note that the respective kinds of processing performed by the signalprocessing unit 900 can be stored in the storing unit as computerprograms to be executed by the arithmetic unit. However, the storingunit in which the programs are stored is a non-transitory recordingmedium. Note that the display controlling unit, the scanning regionsetting unit, and the signal processing unit may be respectivelyconfigured of separate circuits and information processing device or maybe configured as functional blocks of one information processing device.

Acoustic Matching Material

The acoustic matching material 1000 is a material for filling a spacebetween the object E and the acoustic detecting elements 300 andacoustically combining the object E and the acoustic detecting elements300. The material is desirably fluid that has acoustic impedance closeto the acoustic impedances of the object E and the acoustic detectingelements 300 and transmits the pulsed light generated by the lightsource 100. Specifically, water, castor oil, gel, or the like can beused.

Typical Shape of the Three-Dimensional Region of Interest

In this embodiment, the scanning of the supporting unit 400 is a spiraltrack. A region formed together with the track of the high-resolutionregion G at this point is a photoacoustic data acquisition region. Inthis embodiment, the data acquisition region formed by the track of thehigh-resolution region G is the typical shape of the three-dimensionalregion of interest. That is, photoacoustic data of a desired region canbe acquired by instructing a size and a position change such that arange desired to be measured is fit on the inner side of the typicalshape.

In this embodiment, to simplify explanation, a region approximated to acylindrical shape is the typical shape of the three-dimensional regionof interest. However, in implementation, a region smaller than an actualmeasurement region may be represented by an approximate shape or a shapeitself of an aggregate of actual tracks of high-sensitivity regions Gmay be reproduced.

FIG. 4 is a diagram showing a state in which the data acquisition regionchanges by a predetermined amount every time a spiral increases by onecircumference. The predetermined amount is a value that can also becalled feature value corresponding to a pitch of a spiral track. Thisvalue is a feature value peculiar to the apparatus determined withreference to the configuration of the scanning unit of the supportingunit.

C1 in FIG. 4 is an XY section of the typical shape based on a spiraltrack of an innermost circumference. Since the circumferential pitch ofthe spiral track is the 10 mm interval as explained above, as the sizeof the XY section of the typical shape, a diameter increases by 10 mmlike C2 and C3 every time the spiral is increased by one circumference.In this way, with a change amount corresponding to the number ofcircumferences of the spiral track set as a predetermined unit (in thisembodiment, an integer times of a 10 mm pitch), the size change of thethree-dimensional region of interest is instructed. When the userinstructs an increase or reduction of the size of the three-dimensionalregion of interest, a region of interest at the time when the spiraltrack is increased or reduced by one circumference is calculated.

FIG. 5 is a diagram showing a sectional shape C1 on the XY plane of theregion of interest in the spiral track. A circle C1 is a circleinscribing an aggregate of tracks of the high-sensitivity regions Gformed up to an outer circumference immediately outside the spiraltrack. In the figure, a dotted line indicates the spiral track.Alternate long and short dash lines indicate the high-sensitivityregions G in respective measurement positions formed when measurement isperformed at an equal interval pitch on the spiral track. P1 indicates afirst sampling point of the innermost circumference. A sampling pointcorresponding to a first circumference from P1 is P2. At this point, thecircle C1 is set to inscribe an aggregate of the high-sensitivityregions G formed in one circumference of the spiral track. Every timethe spiral track increases by one circumference, not-shown circles C2and C3 are set in the same manner. Then, concentric circles expanding ata 10 mm pitch are obtained.

In this embodiment, as explained above, the typical shape is changedaccording to designation of expansion and reduction of the region ofinterest. A change in the region of interest is three-dimensionallyshown in FIG. 6. R1 is a cylindrical region formed by the region ofinterest C1 on the innermost circumference side. R2 and R3 arecylindrical regions based on C2 and C3. When expansion by one stage isinstructed for the region of interest of R1, the R2 region extended byone circumference of the spiral track is displayed. When expansion ofone more stage is instructed, the R3 region further extended by onecircumference of the spiral track is displayed.

Setting and Measurement of the Three-Dimensional Region of Interest

A process for deciding the three-dimensional region of interest and anacquisition method for a photoacoustic wave carried out on the basis ofthe set region of interest are explained. Steps of a flowchart of FIG. 7are referred to according to necessity.

First, the object E is inserted into a container of the supporting unit400 and the acoustic matching material 1000 is filled (step S1).

An example of an initial screen of the display unit 601 in thisembodiment is shown in FIG. 3. On the display unit 601, as an initialscreen 6011, capture camera images (reference numerals 6012, 6013, and6014) of the object E are displayed. On the camera images, a typicalshape of a three-dimensional region of interest is superimposed anddisplayed in an initial size (step S2).

A display screen in this embodiment is observation images from threedirections by not-shown three capture cameras. However, the displayscreen may be images observed from two directions or may be asuperimposed image of the typical shape of the three-dimensional regionof interest with respect to a perspective view of the apparatus bysimplified illustration.

The size of the typical shape (the three-dimensional region of interest)can be changed according to an expansion or reduction instruction of theuser. Specifically, the user inputs an increase or reduction instructionfor the size of the typical shape of the three-dimensional region ofinterest while viewing the capture camera images of the object E (stepS3). The display controlling unit 600, which receives the size increaseor reduction instruction for the region of interest, changes the size ofthe three-dimensional region of interest with a predetermined changeamount based on a change amount of the measurement region in which thespiral track is increased or reduced in a unit of one circumference. Thedisplay controlling unit 600 updates the display of the display unit 601with an image obtained by superimposing a three-dimensional region ofinterest obtained anew on the capture camera images of the object E(step S4).

The change of the typical shape at this point is performed stepwise withreference to a feature value (e.g., a pitch of the scanning unit)peculiar to the apparatus. That is, as shown in FIG. 6, the size changeof the three-dimensional region of interest is performed by expanding orreducing the cylindrical region of interest with reference to the pitch10 mm for one circumference of the spiral track and updating the regionof interest. For the purpose of causing the user to be aware that thesize of the typical shape is changed stepwise, a shape of a userinterface displayed on the screen 6011 may be determined. For example,if a button with an upward arrow displayed thereon and a button with adownward arrow displayed thereon are displayed on the screen, the usercan easily select an increase or reduction of the size. Alternatively,it is also preferable to select an increase or reduction with a wheel ofa mouse.

At the same time, the user can select the three-dimensional region ofinterest displayed on the display unit 601 with input means, perform aninput for moving a position relatively to the object E, and adjusts theposition of the region of interest. The position adjustment may beperformed before the size of the region of interest is decided. At thispoint, the input of the position moving instruction may be selection anddrag operation by a touch panel of a pointing device such as a mouse ormay be designation by an actual coordinate input or cursor operation.

When the user ends the selection of the three-dimensional region ofinterest, photoacoustic measurement for the set three-dimensional regionof interest is started (step S5).

The scanning region setting unit 700 calculates a spiral track range ofthe supporting unit 400 on the basis of the set three-dimensional regionof interest. The scanning region setting unit 700 receives, concerningthe three-dimensional region of interest designated by theregion-of-interest designating unit, an input of a coordinate value ofthe region of interest and size information indicating how many stagesof expansion or reduction is performed with respect to a default size ofthe region of interest, calculates a measurement range, and decides ascanning track. When an instruction for moving the region of interest isgiven, the scanning region setting unit 700 also reflects theinstruction on the scanning track.

The scanner 800 moves the supporting unit 400 according to the scanningtrack decided by the above procedure. Photoacoustic measurement isexecuted as explained below in positions during the movement. Note thatlight emission and acoustic wave detection may be carried out in stoppositions while the supporting unit repeats a stop and movement or maybe carried out while the supporting unit continuously moves.

In a first measurement position, light irradiated by the light source100 using the optical system 200 is made incident on the object E viathe acoustic matching material 1000. As a result, a photoacoustic waveis generated by a photoacoustic effect due to the light absorbed in theobject E.

The photoacoustic wave generated in the object E is received by theacoustic detecting elements 300 via the acoustic matching material 1000and converted into an electric signal.

The converted electric signal is sent to the signal processing unit 900and stored in a storage device such as a memory in association withmeasurement position information. Consequently, a first electric signalin the first measurement position is stored.

Subsequently, the supporting unit 400 is moved by the scanner 800 to asecond measurement position present on the inner side of the scanningregion set by the scanning region setting unit 700. In the same manneras the measurement in the first measurement position, a second electricsignal in the second measurement position is acquired and stored.

Thereafter, according to a process same as the process explained above,electric signals in all measurement positions in the scanning region setby the scanning region setting unit 700 are acquired. Images of measuredregions are generated by the signal processing unit 900.

As explained above, the apparatus in this embodiment presents thetypical shape of the three-dimensional region of interest to the user.The user viewing the typical shape of the three-dimensional region ofinterest can set the three-dimensional region of interest by increasingor reducing the size of the predetermined shape with the predeterminedchange amount. As a result, it is possible to easily set thethree-dimensional region of interest. Consequently, in the setting ofthe region of interest, the user can set the three-dimensional region ofinterest while being aware of the scanning region without directly beingaware of the change amount of the measurement range related to thedesign and the configuration of the apparatus. As a result, it ispossible to reduce a problem in that a measurement time is long becausea set region is slightly large and in that an unexpected unnecessaryregion is scanned.

Modification

In this modification, a method of extending the configuration explainedin the first embodiment to another form while maintaining the essence ofthe present invention is explained. In this modification, in particular,a scanning method of the supporting unit is different from the scanningmethod in the first embodiment.

In acquiring an acoustic wave generated from the object, the method ofmoving the supporting unit is not limited to the spiral shape. Forexample, a wide region can be measured even if the method is a scanmethod for repeating main scanning for moving the supporting unit in along distance from an end to an end of the region of interest andsub-scanning for moving the supporting unit in a direction crossing(typically, orthogonal to) the main scanning direction. In this case,measurement concerning a stripe, which is an elongated belt-like region,is performed every time the main scanning is performed once and aplurality of the stripes are connected in the sub-scanning direction tomeasure the entire region of interest. In the case of this modification,the stripes are laid one on top of another in order to cover the regionof interest. Therefore, the feature value peculiar to the apparatus is avalue based on the shape and the size of the stripes.

In such vertical and horizontal scan, when the user instructs a sizechange for the shape of a typical three-dimensional region of interestdisplayed to be superimposed on an initial object image, a situationsame as the situation in the first embodiment occurs. That is, when theuser instructs size expansion, if an expanded portion protrudes from astripe of the initial three-dimensional region of interest, an increasein the number of stripes to be scanned is necessary.

Therefore, in this modification as well, a method of easily setting aregion while being aware of a scanning region can be presented to theuser by changing the size of the region of interest stepwise accordingto an input value of the user from the input unit and a change amountpeculiar to the apparatus. As a result, convenience for the user isimproved. It is possible to reduce a measurement time and reduce aburden on an examinee.

Other Embodiments

Embodiments of the present invention can also be realized by a computerof a system or apparatus that reads out and executes computer executableinstructions recorded on a storage medium (e.g., non-transitorycomputer-readable storage medium) to perform the functions of one ormore of the above-described embodiment(s) of the present invention, andby a method performed by the computer of the system or apparatus by, forexample, reading out and executing the computer executable instructionsfrom the storage medium to perform the functions of one or more of theabove-described embodiment(s). The computer may comprise one or more ofa central processing unit (CPU), micro processing unit (MPU), or othercircuitry, and may include a network of separate computers or separatecomputer processors. The computer executable instructions may beprovided to the computer, for example, from a network or the storagemedium. The storage medium may include, for example, one or more of ahard disk, a random-access memory (RAM), a read only memory (ROM), astorage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2014-127662, filed on Jun. 20, 2014, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An object information acquiring apparatus comprising: a light source; an irradiating unit configured to irradiate an object with light from the light source; a plurality of detecting elements configured to detect an acoustic wave propagated from the object and output an electric signal; a processing unit configured to acquire characteristic information of an inside of the object using the electric signal; a supporting unit configured to support the plurality of detecting elements; an input unit capable of receiving an input of information concerning a region of interest, which is a three-dimensional region where the characteristic information is to be acquired; a display controlling unit configured to cause a display unit to display a predetermined three-dimensional shape representing the region of interest; a scanning region setting unit configured to set a scanning region on the basis of the region of interest; and a scanning unit configured to move the supporting unit in the scanning region, wherein the display controlling unit changes, on the basis of the information concerning the region of interest input from the input unit, a size of the region of interest stepwise by using a feature value peculiar to the apparatus as a unit, and causes the display unit to display the region of interest after the change.
 2. The object information acquiring apparatus according to claim 1, wherein the input unit receives an instruction for setting the scanning region on the basis of the region of interest displayed on the display unit, and when receiving the instruction for setting the scanning region input from the input unit, the scanning region setting unit sets the scanning region on the basis of the region of interest displayed on the display unit.
 3. The object information acquiring apparatus according to claim 1, wherein the display controlling unit causes the display unit to display the scanning region set by the scanning region setting unit.
 4. The object information acquiring apparatus according to claim 1, wherein the scanning unit spirally moves the supporting unit.
 5. The object information acquiring apparatus according to claim 4, wherein the predetermined three-dimensional shape representing the region of interest is a columnar shape, and the feature value peculiar to the apparatus is a circumferential pitch of the spiral.
 6. The object information acquiring apparatus according to claim 1, wherein the input unit can receive designation of an increase or reduction of a size of the predetermined three-dimensional shape.
 7. The object information acquiring apparatus according to claim 1, wherein the input unit can receive designation of movement of the predetermined three-dimensional shape.
 8. The object information acquiring apparatus according to claim 1, wherein the supporting unit supports the plurality of detecting elements such that directional axes of at least a part of the plurality of detecting elements converge.
 9. The object information acquiring apparatus according to claim 8, wherein the scanning region setting unit sets the scanning region such that the region of interest includes high-sensitivity regions where the directional axes of the plurality of detection elements converge.
 10. The object information acquiring apparatus according to claim 8, wherein the scanning unit spirally moves the supporting unit, and the predetermined three-dimensional shape representing the region of interest is a shape of an aggregate of tracks of the high-sensitivity regions.
 11. The object information acquiring apparatus according to claim 1, further comprising the display unit. 